UNIVERSITY    OF   CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL    EXPERIMENT    STATION 

BERKELEY,  CALIFORNIA 


FIG   SMUT 

BY 
EDITH  H.  PHILLIPS,  ELIZABETH  H.  SMITH  and  RALPH  E.  SMITH 


BULLETIN  No.  387 

April,  1925 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY,  CALIFORNIA 

1925 


FIG  SMUT 

By  EDITH  H.  PHILLIPS,  ELIZABETH  H.  SMITH  and  EALPH  E.  SMITH 


CONTENTS 

PAGE 

The  problem 4 

Natural  advantages  of  the  fig  industry 4 

What  is  the  matter  with  figs 4 

History  and  purpose  of  this  investigation 5 

Varieties  and  peculiarities  of  the  fig 5 

What  is  fig  smut 6 

Occurrence  of  smut 8 

Varieties  affected 9 

The  cause  and  history  of  smut 9 

Opinion  of  an  authority 11 

Comparison  of  the  fig  smut  fungus  with  other  strains  of  Aspergillus  from 

the  San  Joaquin  Valley 12 

Inoculations 15 

The  fig  smut  fungus  is  the  common  Aspergillus  niger  and  not  a  distinct  species..  15 

When  do  figs  become  infected  with  smut 15 

Inoculations 16 

Time  of  natural  infection 21 

In  what  part  of  the  fig  does  the  infection  take  place 23 

Where  do  smut  spores  come  from 23 

How  do  smut  spores  get  into  the  fig 23 

Wind 23 

Insects 24 

Dried  fruit  beetle 25 

Further  investigations  on  the  relations  between  fig  diseases  and  the 

dried  fruit  beetle 28 

Blister  mite 32 

Other  insects 32 

Control  of  smut 33 

Spraying 33 

Fertilization  and  soil  treatment 35 

Sanitation 36 

Immune  varieties 36 

Conclusions 37 


4  UNIVERSITY    OF    CALIFORNIA- — EXPERIMENT    STATION 

THE  PROBLEM 

NATUEAL  ADVANTAGES  OF  THE  FIG  INDUSTRY 

The  fig  deserves  to  be  one  of  California's  best  commercial  fruits. 
It  shares  with  the  olive  and  grape  the  distinction  of  being  one  of  the 
oldest  cultivated  fruits.  It  is  nutritious,  appetizing,  of  attractive 
appearance  and  wholesome.  The  fruit  has  a  great  variety  of  uses,  not 
only  in  the  usual  dried  form,  but  also  for  eating  fresh  and  in  such 
manufactured  forms  as  jam,  marmalades,  preserves,  canning,  candy, 
bakery  products,  breakfast  and  health  foods,  beverages  and  medicinal 
preparations.  The  well  known  salutary  properties  of  dried  figs  lend 
themselves  particularly  well  to  advertising.  The  fig  is  one  of  the 
healthiest  of  fruit  trees,  easily  suited  as  to  soil  and  moisture,  and  well 
adapted  to  a  wide  area  in  California  and  (for  dried  figs)  to  no  other 
portion  of  the  United  States.  The  quality  of  California-grown  figs  at 
their  best  is  admittedly  unsurpassed. 

And  yet,  it  must  be  said  that  fig  culture  is  not  so  well  established 
in  California  as  that  of  many  other  fruits  and  considerable  difficulty 
is  experienced  in  disposing  of  the  comparatively  small  dried  fig  crop 
of  the  state  at  even  moderate  prices.  California  produces  less  than 
10,000  tons  of  dried  figs  per  annum  (9000  tons  in  1923)  as  compared 
with  25,000  tons  of  walnuts,  100,000  tons  of  prunes,  and  250,000  tons 
of  raisins.  Even  though  foreign  competition  is  keen,  exchange  rates 
low,  and  fig  production  in  the  Mediterranean  countries  very  large,  it 
seems  remarkable  that  this  small  tonnage  of  California-grown  figs 
cannot  readily  be  marketed  at  good  prices. 

WHAT  IS  THE  MATTER  WITH  FIGS 

The  greatest  obstacle  to  the  success  of  the  fig  industry  at  the  present 
time  is  the  occurrence  of  various  forms  of  rotting,  souring,  and  molding 
of  the  fruit,  which  at  times  become  very  abundant  and  troublesome  and 
for  which  no  method  of  control  has  been  found.  Such  defects  reduce 
yields  and  make  it  very  difficult  to  put  up  a  high-grade,  dependable 
pack  of  sufficient  quality  to  compete  on  better  than  even  terms  with 
the  foreign  product  and  one  upon  which  the  arts  of  advertising  and 
salesmanship  can  confidently  be  practiced.  It  is  only  by  such  adver- 
tising, backed  by  superior,  uniform  quality  that  our  increased  produc- 
tion of  other  foreign-competing  fruit  products  has  been  successfully 
marketed. 


Bull.  387]  FIG  gMUT 


HISTORY  AND  PURPOSE  OF  THIS  INVESTIGATION 

Soon  after  the  formation  of  the  cooperative  fig  marketing  organiza- 
tion, ''The  California  Fig  Growers"  (afterwards  merged  into  the 
"California  Peach  and  Fig  Growers,  Inc."),  the  directors  of  the  asso- 
ciation felt  that  more  information  about  the  nature  and  control  of 
these  troubles  was  urgently  needed  for  the  welfare  of  the  industry. 
The  disease  called  "smut"  first  attracted  attention  on  account  of  its 
conspicuous  nature.  The  senior  writer  was  accordingly  employed  by 
the  Association  in  December,  1920,  to  investigate  this  problem.  The 
first  year 's  work  was  at  the  expense  of  the  Association.  After  Decem- 
ber, 1921,  the  investigation  was  supported  by  the  Agricultural  Experi- 
ment Station  of  the  University  of  California,  with  the  cooperation  of 
the  Association.  This  work  was  done  mainly  at  Fresno,  California,  and 
in  the  Plant  Pathology  laboratory  at  Berkeley. 

Credit  is  due  to  many  fig  growers  and  others  for  assisting  in  this 
work.  Particular  mention  must  be  made  of  Mr.  I.  J.  Condit  of 
the  California  Peach  and  Fig  Growers,  who  has  been  of  constant  aid 
in  carrying  out  the  experiments,  and  who  also  furnished  several  of  the 
illustrations.  Messrs.  Markarian  of  the  Markarian  Fig  Gardens, 
Fresno,  and  Glotzbach  of  the  Burleigh  Ranch  near  Fresno,  offered  to 
the  writers  every  facility  for  work  in  their  orchards,  and  a  large  part 
of  the  work  reported  in  this  bulletin  was  done  in  these  two  places.  The 
assistance  and  cooperation  rendered  by  many  other  growers  is  hereby 
gratefully  acknowledged. 


PECULIARITIES  AND  VARIETIES  OF  THE  FIG 

The  fruit  of  the  fig  is  an  enlarged,  hollow  receptacle  or  flower  base, 
with  a  small  opening  at  the  apical  end.  The  little  individual  flowers 
are  borne  closely  crowded  together  on  the  inner  surface.  Figure  7 
gives  a  good  idea  of  this  structure.  When  fertile  seed  are  produced, 
pollination  is  effected  only  through  the  agency  of  the  Blastophaga 
insects,  which  bring  the  pollen  from  the  staminiferous,  non-edible 
Caprifigs  in  which  they  breed.  Some  varieties  of  figs  set  no  fruit  with- 
out such  pollination,  while  other  kinds  produce  abundant  fruit  without 
pollination  but  contain  no  fertile  seeds.  The  word  caprification  is 
commonly  used  to  designate  the  process  of  pollination  effected  by  the 
insect.    If  caprification  happens  to  take  place  in  those  varieties  which 


6  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

do  not  require  it,  the  figs  contain  fertile  seeds  and  have  a  somewhat 
different  character  from  the  uncaprifiecl  specimens.  From  the  stand- 
point of  disease,  important  variations  exist  in  the  structure  of  the  fruit 
in  different  varieties  of  figs,  relating  especially  to  the  size  of  the 
terminal  opening  and  that  of  the  interior  cavity.  Of  the  many  different 
fig  varieties,  four  are  commonly  grown  in  the  San  Joaquin  Valley  of 
California.  The  Calimyrna  is  the  true  Smyrna  type  of  fig,  requiring 
caprification.  The  Adriatic  is  a  white,  non-caprified  variety  grown 
extensively  for  drying.  The  Mission  is  a  black,  non-caprified  fig  used 
for  both  fresh  and  dried  fruit,  and  noted  for  the  vigor  and  hardiness 
of  the  tree.  The  Kadota  (which  is  properly  the  Italian  variety 
Dotatto)  is  a  small,  white,  non-caprified  fig  grown  especially  for  pre- 
serving. The  fruit  of  the  Mission  and  Kadota  has  a  solid  center  with 
little  interior  cavity  and  a  small,  closed  eye,  while  in  the  Calimyrna 
and  Adriatic  the  eye  and  (in  the  Adriatic)  the  inside  cavity  are  rather 
open.  The  importance  of  these  differences  will  appear  later  in  con- 
nection with  the  relation  of  insects  to  fig  smut  and  other  diseases. 


WHAT  IS  FIG  SMUT 

Typical  smut  in  dried  figs  occurs  as  a  black,  powdery  mass  in  the 
pulp  of  the  fruit  (fig.  1,  A).  The  mass  is  composed  of  fungous  spores. 
On  squeezing  such  fruits  the  spores  shoot  out  for  a  considerable  dis- 
tance from  the  eye  in  a  black  cloud,  while  fruits  less  attected  show  dark 
or  yellowish  spots  in  the  pulp  with  no  spores.  The  skin  of  many  of 
the  badly  smutted  figs  has  a  dark,  translucent  appearance  by  which 
they  are  easily  picked  out,  but  others,  especially  those  with  pulp  only 
slightly  affected,  show  no  external  evidence  of  disease,  and  so  reach  the 
market.  It  is  only  on  tearing  open  such  figs  that  the  smut  is  discovered. 
Tests  have  shown  that  smutty  figs  are  not  injurious  when  eaten,  but  the 
appearance  of  such  figs  is  disgusting  and  the  finding  of  one  in  a  pack- 
age is  often  enough  to  cause  the  whole  lot  to  be  thrown  away  and  the 
purchaser  to  hesitate  before  again  buying  California  dried  figs.  The 
discovery  of  a  smutty  fig  in  the  preserved,  fresh  fruit  by  cutting  into 
it  with  a  spoon  and  seeing  the  inky  contents  run  out  into  the  clear 
syrup,  is  even  more  disgusting.  This  has  a  serious  effect  on  con- 
sumption, although  the  number  of  smutty  figs  occurring  either  in 
packages  of  the  dried  fruit  or  in  the  preserved  products  is  extremely 
small  and  the  actual  loss  of  material  is  insignificant. 


Bull.  387 


FIG    SMUT 


r 


B 


-  f  * 


fv*9Kffi| 


Fig.  1. — Fig  Smut.    (A)  Interior,  mature  fig.    (B)  Exterior  fresh  figs  on  tree. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


OCCURRENCE  OF  SMUT 

As  is  well  known  to  growers  smut  may  be  found  in  figs  in  the 
drying  yard  and  even  while  they  are  still  hanging  on  the  tree.  In 
such  places  there  is  sometimes  a  considerable  percentage  of  affected 
fruit,  particularly  in  the  first  pickings.  Many  of  the  smutty  figs  can 
quite  readily  be  thrown  out  when  they  are  gathered  from  the  ground. 
They  are,  however,  mixed  with  culls  of  various  other  kinds  more 
numerous  than  the  smutty  specimens.     While  the  smut-affected  figs 


Fig.  2. — Fresh  fig,  with  rot  caused  by  smut  fungus. 

are  still  on  the  tree,  some  of  them  can  quite  easily  be  detected  by  the 
discoloration  and  soft  rot  at  the  eye  end  (fig.  1  B,  and  fig.  2).  Others 
cannot  be  distinguished  from  the  good  figs  without  breaking  them  open. 
The  effect  of  the  disease  on  fresh  figs  is  very  characteristic.  Both 
skin  and  pulp  are  affected,  starting  round  the  eye.  The  color  is  dirty 
white  or  slighly  pinkish,  the  texture  fairly  firm,  stiffening  and  thicken- 
ing up  somewhat  to  a  cheesy  consistency.  The  surface  of  the  skin  is 
clean  except  in  rare  cases  of  contacts,  but  a  mass  of  white  mycelium 
develops  in  the  pulp  with  final  formation  of  pockets  lined  with  the 
characteristic  black  spore  masses.  In  late  infections  the  spores  are 
formed  earlier  and  the  pulp  only  is  affected,  which  accounts  for  the 
difficulty  in  eliminating  all  of  the  smutted  figs  during  sorting. 


Bull.  387]  FIG  smut 


VARIETIES  AFFECTED 

No  kind  of  fig  is  entirely  immune  to  smut,-  but  the  Black  Mission 
and  Kadota  varieties  are  much  less  affected  than  the  Adriatic  and 
Calimyrna. 


THE  CAUSE  AND  HISTORY  OF  SMUT 

Examination  with  the  microscope  shows  that  the  black  mass  in 
the  inside  of  smutty  figs  is  composed  of  a  fungous  growth  (mycelium) 
and  spores,  resembling  that  which  is  technically  called  Aspergillus 
niger.  This  fungus  is  a  black  mold  which  is  very  common  on  all  kinds 
of  decaying  vegetable  matter.  It  is  not  a  true  smut  like  that  of  grain, 
but  is  given  this  name  on  account  of  its  superficial  resemblance  to  the 
latter  disease.  Examination  of  the  literature  shows  that  a  similar 
condition  in  figs  has  been  known  in  Europe  for  a  long  time.  In  1867 
Reichardt,1  studying  a  fig  smut  apparently  similar  to  ours,  described 
a  fungus  which  he  named  Ustilago  ficuum  as  the  cause  of  the  disease. 
This  was  found  in  figs  imported  from  Asia  Minor  into  Europe. 
Hennings,2  correcting  the  idea  that  this  was  a  true  smut  (Ustilago), 
named  it  Sterigmatocystis  ficuum.  Wehmer3  (p.  107),  set  aside  the 
distinction  between  Sterigmatocystis  and  Aspergillus  and  named  this 
fungus  A.  ficuum.  A  similar  fungus  found  on  dates  from  North 
Africa  was  first  named  Ustilago  phoenicis  by  Corda4  (p.  9,  fig.  26)  in 
1840.  This  name  was  changed  in  1891  to  Sterigmatocystis  phoenicis 
by  Patouillard  and  Delacroix,5  and  later  by  Wehmer3  to  Aspergillus 
phoenicis.  Von  Lagerheim6  considered  this  date  fungus  to  be  the 
same  as  Aspergillus  ficuum  of  the  fig.  Thorn  and  Currie7  concluded 
that  Aspergillus  niger,  as  commonly  understood,  represents  a  some- 
what indefinite  and  unstable  group,  containing  many  strains  and  more 


i  Reichardt,  H.  W.  Ein  neuer  Brandpilz.  In  Zool.-Bot.  Ges.  Wien.  17: 
335-336.     1867. 

2  Hennings,  P.  Ustilago  Ficuum  Eeicli.  —  Sterigmatocystis  Ficuum  (Keich.) 
P.  Henn.     In  Hedwigia  34:  86-87.     1895. 

3  Wehmer,  C.  Die  Pilzgattung  Aspergillus.  In  Mem.  Soc.  Phys.  et  d'Hist. 
Nat.  Geneve  33:  (Pt.  II,  no.  4)  1-157,  tab.  1-5.     1901. 

4  Corda,  C.    In  Icon.  Fung.  4:  1-53,  ills,     1840. 

5  Patouillard,  M.,  and  Delacroix,  G.  Sur  une  maladie  des  Dattes  produite 
par  le  Sterigmatocystis  Phoenicis  (Corda)  Patouill.  et  Delacr.  In  Bull.  Soc.  Myc. 
France  7:  118-120,  plate  IX.     1891. 

6  Von  Lagerheim,  G.     In  Svensk  Farmaceut.     Tidskrift,  no.  18,  ills.     1903. 

7  Thorn,  C,  and  Currie,  J.  N.  Aspergillus  Niger  Group.  In  Jour.  Agr.  Ees. 
7:  1-15.     1916. 


10 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


or  less  distinct  forms.  The  strains  which  they  studied  as  representing 
A.  ficuum  and  A.  phoenicis  were  found  to  be  within  the  group  and  not 
sufficiently  distinguished  to  be  considered  distinct  species.  They  found 
it  impossible  to  distinguish  Sterigmatocystis  as  a  separate  genus.  In 
California  fig  smut  has  been  known  for  some  time  and  the  fungus  so 
regularly  associated  with  it  has  been  called  Sterigmatocystis  or 
Aspergillus,    without    any    more    specific    identification    (Hodgson8). 


Fig.  3. — Typical  spore  head  of  a  species  of  Aspergillus;  much  enlarged. 


Numerous  cultures  and  inoculations  made  by  the  writers  in  connec- 
tion with  various  experiments  reported  in  this  bulletin  show  that  a 
fungus  of  the  black  Aspergillus  type  is  the  specific  cause  of  fig  smut. 
The  question  of  the  proper  use  of  the  names  Aspergillus  and 
Sterigmatocystis  will  not  be  considered  here,  but  the  former  name 
will  be  used  for  our  fungus  and  related  forms.  Aspergillus  niger  is 
one  of  the  commonest  molds  occurring  on  decaying  fruit  and  organic 


s  Hodgson,  E.  W.     Black  Smut  of  Figs.     In  Monthly  Bull.  Cal.  State  Dept. 
Agr.  7:  188-189,  1  fig.     1918. 


Bull.  387] 


FIG    SMUT 


11 


matter  in  all  parts  of  California  and  elsewhere  (figs.  3  and  4).  In 
considering  the  cause  and  particularly  in  relation  to  the  control  of  fig 
smut,  it  is  very  important  to  know  whether  the  fungus  is  the  ordinary, 
universally  abundant  A.  niger,  or  whether  it  may  possibly  be  a  distinct 
species  or  even  strain  which  occurs  only  on  the  fig. 


Fig.  4. — Cultures  of  A.  niger,  made  from  pulp  of  figs  of  type  5  (see  p.  16), 

Natural  size. 


OPINION  OF  AN  AUTHORITY 

A  culture  of  the  fungus  from  a  typically  smutty  fig  was  sent  to 
Mr.  Charles  Thorn  of  the  United  States  Department  of  Agriculture, 
and  the  following  reply  received :  "Your  black  Aspergillus  has  spores 
typical  in  marking  and  about  4  microns  in  diameter.  There  is  no 
particular  reason  for  separating  it  from  the  standard  Aspergillus 
niger." 


12 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


COMPARISON  OF  THE  FIG  SMUT  FUNGUS   WITH  OTHER  STRAINS  OF 
ASPERGILLUS  FROM  THE  SAN  JOAQUIN  VALLEY 

In  the  district  where  fig  smut  occurs,  a  black  mold  of  the  same 
general  appearance  as  the  smut  fungus  is  very  common  on  all  sorts  of 
vegetable  material.  This  is  true  of  ripe  fruit  of  many  different  kinds, 
decaying  fruits  and   vegetables   and  the  stems   and  leaves  of  plant 


Fig.  5. — Smut  fungus  (S)  as  caught  from  air  with  other  fungi  on  culture  plate. 

remains  (fig.  6).  There  is  also  one  quite  definite  fruit  decay  disease 
of  a  similar  nature  to  fig  smut.  This  is  the  so-called  smut  or  black 
rot  of  the  fruit  of  the  pomegranate,  caused  by  a  black  Aspergillus. 
Cultures  were  obtained  from  each  of  the  following  sources:  1.  From 
spores  floating  in  the  air  of  a  fig  orchard,  caught  by  exposing  culture 
plates,  Fresno,  September,  1921   (see  fig.  5,  8).     2.  From  growth  on 


Bull.  387] 


FIG    SMUT 


13 


Fig.  6. — Smut  fungus.     (A)  On  apricot.     (B)  On  fig  twig.     (C)  On  grapes. 


14  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

dead  fig  twigs,  Fresno,  August,  1921  (see  fig.  6,  B).  3.  From  rotten 
spots  on  surface  of  fresh  fig,  Fresno,  August,  1920.  4.  Diseased  dahlia 
stem,  Fresno,  1921.  5.  From  inside  ripe  peach,  Dinuba,  August,  1921. 
6.  Ripe  peach,  Fresno,  August,  1921.  7  Dried  fig  with  typical  smut, 
Fresno,  September,  1921-  8.  Dried  raisins  in  cartons,  Fresno,  October, 
1921.  9.  Dry  onions,  Fresno,  October,  1921.  10.  Dry  onions,  Berke- 
ley, September,  1921.  11.  Pomegranate  smut  fungus,  October,  1921. 
These  isolations  or  strains  were  studied  comparatively  for  the  purpose 
of  finding  out  whether  or  not  the  fig  smut  fungus  is  identical  with  the 
ordinary  black  mold,  Aspergillus  niger,  which  occurs  so  commonly  on 
other  materials. 

Cultures  of  the  eleven  strains  were  grown  under  identical  conditions 
on  the  following  media.  In  this  experiment  the  usual  technical 
methods  were  employed. 

(1)  Czapek's  agar  with  glucose  instead  of  sucrose. 

(2)  Carrot  gelatine. 

(3)  Prazmowski's  agar. 

(4)  Sound  Newtown  Pippin  apples. 

(5)  Nutrient  gelatine. 

(6)  Fig  agar. 

(7)  Raulin's  solution. 

(8)  Hard  lima  bean  agar. 

(9)  Hard  potato  agar. 

(10)  Shear's  corn  meal  agar. 

(11)  Non-nutrient  agar. 

(12)  Raw  orange  pulp. 

(13)  Raw  potato  slices. 

A  large  amount  of  work  was  involved  in  this  experiment,  in  pre- 
paring the  various  culture  media  and  observing  and  recording  the 
results  in  detail.  For  the  purpose  of  this  publication,  however,  it  is 
sufficient  to  say  that  on  each  medium  all  the  fungi  behaved  and 
appeared  exactly  alike,  except  number  11,  the  pomegranate  strain, 
which  showed  a  constant  difference  from  the  others.  The  spore  stalks 
were  taller,  the  spores  and  spore  heads  larger,  and  the  spores  more 
roughened.  From  the  result  of  this  experiment  it  appears  that  in  its 
form,  structure  and  appearance  when  growing  on  each  of  the  media 
tested,  the  fig  smut  fungus  cannot  be  distinguished  from  the  ordinary 
Aspergillus  niger,  but  that  the  form  obtained  from  the  pomegranate 
used  in  this  experiment  is  a  distinct  type  or  species,  Hodgson8  states 
that  "cross  inoculation  into  pomegranates  has  shown  that  the  fig 
Sterigmatocystis  is  the  same  as  the  organism  causing  internal  rot  of 


Bull.  387]  FIG  gMUT  15 

pomegranates."  This  does  not  necessarily  follow,  however,  for  even 
though  infection  of  the  pomegranate  with  Aspergillus  niger  is  possible, 
the  same  is  true  of  many  other  fungi.  Our  results  suggest  that  the 
pomegranate  smut  fungus  may  be  a  different  species  from  that  of  the 
ng. 

INOCULATIONS 

For  further  evidence  on  the  identity  of  the  smut  fungus,  figs  at 
different  stages  of  ripeness  were  inoculated  with  spores  from  cultures 
of  strains  number  1  (from  air),  2  (fig  twig),  3  (fresh  fig),  5  (ripe 
peach),  8  (raisin)  and  11  (pomegranate).  This  and  similar  experi- 
ments were  made  and  repeated  many  times  in  1921  and  1922.  In 
making  the  inoculations,  a  few  spores  were  placed  inside  of  the  eye 
of  the  fig  with  a  needle.  Inoculations  were  made  on  all  the  common 
fig  varieties,  Calimyrna,  Mission,  Adriatic,  and  Kaclota.  In  virtually 
every  case,  typical  fungus  development  and  smut  occurred.  The  pome- 
granate fungus  continued,  however,  to  show  its  peculiar  characteristics. 


THE  FIG  SMUT  FUNGUS  IS  THE   COMMON  ASPERGILLUS 
NIGER  AND  NOT  A  DISTINCT  SPECIES 

The  statement  by  Mr.  Thorn  and  the  results  of  comparative  cultures 
and  inoculations  all  indicate  that  the  fungus  which  causes  fig  smut  is 
not  a  specific  strain  or  species  of  Aspergillus,  but  that  A.  niger,  a  mold 
which  is  common  everywhere  in  the  air,  soil  and  on  decaying  fruit  and 
vegetable  matter  of  all  kinds,  is  the  usual  cause  of  the  infection. 


WHEN  DO  FIGS  BECOME  INFECTED  WITH  SMUT 

At  the  beginning  of  this  investigation,  little  was  known  as  to  when 
the  smut  fungus  infects  the  fig,  except  that  some  figs  become  infected 
while  still-  on  the  tree.  Many  thought  that  the  bulk  of  the  infection 
occurred  in  the  drying  trays  or  even  at  the  packing  house  and  that 
some  process  of  dipping  or  treatment,  or  quick  drying  at  harvest  time, 
might  prevent  most  of  the  trouble. 


16  UNIVERSITY    OF    CALIFORNIA- — EXPERIMENT    STATION 


INOCULATIONS 

During  the  season  of  1921  many  experiments  were  made  in  inoculat- 
ing dried,  nearly  dry,  soft-ripe,  and  green  figs  with  the  fungus.  It 
was  found  that  Aspergillus  failed  to  grow  and  no  smut  developed  on 
dried  or  partly  dried  figs,  but  abundant  fungus  growth  and  typical 
smut  was  produced  in  figs  by  inoculations  at  any  stage  up  to  a  time 
just  before  they  commenced  to  soften,  shrivel,  and  fall  from  the  tree. 
It  was  found  to  be  impossible  to  produce  smut  by  inoculating  figs  after 
the  fruit  is  dry  enough  to  drop.  Before  the  figs  begin  to  soften  they 
can  be  inoculated  with  the  fungus  and  typical  rot  produced  even  when 
the  fruit  is  still  small  and  green.  From  these  earlier  inoculations  it 
appeared  therefore  that  smut  must  start  at  some  time  when  the  figs 
are  still  on  the  tree  and  before  they  commence  to  dry  much. 

The  question  of  the  time  when  figs  naturally  become  infected  with 
smut  was  investigated  in  1921.9  In  order  to  systematize  the  work  and 
establish  a  basis  for  reference,  a  series  of  ten  types  of  figs  was  arbi- 
trarily chosen,  each  type  representing  a  stage  in  the  ripening  of  the 
fruit.  These  types  or  stages  are  represented  in  figures  7,  8,  and  9  and 
may  be  described  as  follows : 

(1)  Fruit  not  quite  full  grown,  still  green  and  hard. 

(2)  Full  grown,  eye  scales  beginning  to  loosen. 

(3)  Eye  fairly  well  opened,  fruit  still  green  and  firm. 

(4)  Slightly  yielding  to  pressure,  pulp  succulent,  but  still  firm. 

(5)  Fig  ripe  as  for  picking  for  fresh  shipment.    No  shriveling,  pulp 

opaque. 

(6)  Skin  slightly  shriveled,  pulp  somewhat  translucent. 

(7)  Distinct  shriveling,  contents  still  red,  not  sticky. 

(8)  Much  shriveled  and  skin  beginning  to  discolor.  Pulp  mahogany 

color,  slightly  sticky. 

(9)  Skin   brown,    but    flexible,    pulp   brown,   translucent,    sticky. 

Stage  of  completed  normal  drying. 
(10)   Over-dry,  stiff,  and  hard.     Flowers  stand  out  separately  in 
pulp. 


o  Smith,  E.  H.,  and  Phillips,  E.  H.  Studies  of  the  So-called  "Smut"  of 
White  Fig  Varieties.  In  Monthly  Bull.  Cal.  State  Dept.  Agr.  11:  755-758, 
figs.  178-180.    1022. 


Bull.  387] 


FIG    SMUT 


17 


Fig.  7 .—stages  of  maturity  in  Adriatic  figs,  types  1,  2,  3,  and  4. 


18 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


As  an  indication  of  the  composition  of  figs  at  these  stages,  especially 
in  regard  to  moisture  and  sugar,  the  following  analyses  by  the  Twin- 
ing Laboratory,  Fresno,  furnished  by  Mr.  I.  J.  Condit  of  the  Fig 
Growers '  Association,  are  of  interest. 


Fig.  8. — Stages  of  maturity  in  Adriatic  figs,  types  5,  6,  and  7. 


Bull.  387] 


FIG    SMUT 


19 


Analyses  of  Adriatic  Figs  at  Different  Stages  of  Maturity 

Type  Moisture  Sugars 

3  83.25%  9.12% 

4  80.80%  12.92% 

5  74.65%  18.87% 

6  61%  33.04% 

7  52.45%  46.36% 

8  42.50%  46.04% 

9  29%  56.85% 


10 


13.10% 


69.58% 


Fig#  9._Stages  of  maturity  in  Adriatic  figs,  types  8,  9,  and  10. 


20  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  increase  in  the  percentage  of  sugar  and  corresponding  decrease 
in  moisture  from  type  4  to  type  6  will  be  noticed. 

All  the  following  experiments  were  carried  on  in  the  vicinity  of 
Fresno,  California,  under  the  low  humidity  conditions  typical  of  the 
summer  season  in  the  San  Joaquin  Valley. 

On  August  18,  1921,  a  thick  suspension  in  water  of  spores  from  a 
smutty  fig  was  made.  In  this  instance  figs  of  the  Kadota  variety  were 
used  for  inoculation.  The  eye  of  the  fig  to  be  inoculated  was  slightly 
opening  by  running  in  a  glass  tube  drawn  to  a  point,  penetrating  the 
fig  to  about  one-fourth  inch.  A  drop  of  the  suspension  was  then  intro- 
duced with  a  pipette,  holding  the  fig  a  few  seconds  in  such  a  way  as  to 
allow  the  water  to  run  in.  After  the  inoculations,  observations  were 
made  every  two  days,  at  first  by  microscopic  examination  before  the 
fungus  became  visible  to  the  eye.  Two  to  four  figs  of  each  type  were 
examined  at  each  time,  four  records  being  taken  in  all. 

On  August  31st  more  inoculations  were  made,  using  Adriatic, 
Kadota,  and  Calimyrna  figs.  Spores  from  pure  cultures  of  the  fungus 
were  employed,  in  some  cases  in  suspension  in  water,  in  others  dry 
spores  were  inserted  into  the  eye  of  the  fig  on  the  point  of  a  sterile 
needle.  Twenty  figs  or  more  of  each  kind  at  different  stages  of 
development  were  inoculated. 

On  September  9th,  inoculations  of  types  6,  7,  8,  and  9  were  made 
in  the  laboratory  because  in  the  orchard  figs  of  these  types  soon  fall 
from  the  tree.  The  figs  used  were  Adriatic,  all  picked  from  the  tree 
except  those  of  type  No.  9  which  had  already  fallen  and  were  picked 
from  the  ground.  Ten  figs  of  each  type  were  inoculated.  Each  fig 
was  carefully  split  in  two  by  cutting  the  skin  all  around  up  to  the  eye, 
not  touching  the  pulp  or  the  eye  itself.  Each  was  inoculated  twice  with 
smut  spores  from  a  pure  culture,  once  just  below  the  eye  and  again 
near  the  neck,  working  the  spores  well  into  the  pulp  with  the  needle. 
The  figs  were  pressed  together  after  inoculation  and  each  fastened  with 
a  toothpick;  then  those  of  each  type  were  placed  together  in  moist 
chambers. 

On  September  17,  1921,  ten  or  more  Adriatic  figs  of  types  6,  7,  8,  9, 
and  10  were  inoculated  in  the  laboratory.  Every  fig  was  split  open 
and  the  inner  surface  covered  with  a  black  smear  of  smut  spores  from 
a  pure  culture.  Some  were  pressed  together  again,  others  left  open. 
Figs  of  each  type  were  then  placed  in  separate  moist  chambers. 

Results  were  very  uniform  in  all  of  these  experiments.  The  fungus 
developed  in  green  figs  of  any  stage,  producing  the  characteristic  rot. 
Figs  of  types  2  to  5  inoculated  on  the  tree  were  badly  rotted  within 
a  week's  time,  some  fruits  of  types  2  and  3  being  almost  entirely 


Bull.  387]  FIG  SMUT  21 

decayed.  Development  was  uncertain  or  scanty  in  types  7  and  8,  in 
which  drying  had  commenced  and  the  sugar  content  high.  In  figs  of 
type  8  the  fungus  did  not  develop  to  any  great  extent,  and  only  when 
the  fruit  was  kept  in  moist  chambers  and  held  for  two  or  three  days. 
In  types  9  and  10,  representing  dried  figs,  there  was  no  development 
whatever.  These  tests  were  probably  more  severe  than  would  occur 
in  natural  infection,  owing  to  the  introduction  of  such  large  numbers 
of  spores. 

These  experiments  show  that  the  rot  and  smut  will  develop  if  the 
fungous  spores  are  introduced  into  figs  at  any  time  up  to  that  when 
the  fruit  begins  to  dry  and  shrivel  and  is  about  ready  to  fall  from  the 
tree,  but  soon  after  it  is  ripe  and  begins  to  dry,  the  fungus  is  no  longer 
able  to  grow  upon  it.  This  indicates  that  practically  all  smutty  figs 
must  become  infected  when  they  are  still  on  the  tree,  rather  than  at 
any  time  after  they  become  fully  ripe  and  fall  to  the  ground  and  that 
the  time  for  any  control  measures  would  have  to  be  before  the  figs 
ripen. 

TIME  OF  NATURAL  INFECTION 

The  fact  that  figs  may  be  artificially  infected  with  smut  at  any  time 
before  they  begin  to  shrivel,  does  not  necessarily  indicate  that  natural 
infection  takes  place  over  the  same  period.  If  natural  infection  with 
smut  occurs  at  any  time  during  the  early  growth  of  the  fruit,  the 
results  of  our  inoculation  experiments  would  suggest  that  many  figs 
would  be  attacked  and  destroyed  by  this  fungus  long  before  they 
reach  maturity.  This  is  not  the  case,  as  very  few  decayed  or  smutted 
figs  are  found  except  those  that  are  virtually  full  grown.  This  indicates 
that  the  spores  do  not  get  in  until  the  figs  are  nearly  full  grown,  and 
consequently  the  smut  does  not  start  until  that  time.  This  question 
was  studied  in  the  following  manner : 

On  August  22-24,  1921,  twenty-eight  Adriatic  figs  of  each  of  the 
types  numbered  from  1  to  8  were  examined  by  cutting  them  in  half 
and  studying  the  interior  with  hand  lens  and  microscope.  Smut  was 
present  in  abundance  in  the  ripe  fruit  on  the  trees  from  which  these 
figs  were  taken.  In  doubtful  cases,  where  uncertainty  existed  as  to 
whether  traces  of  smut  were  seen,  plate  cultures  in  fig  agar  were  made 
from  the  suspected  tissue.  The  result  of  these  examinations  showed 
that  no  smut,  either  spores  or  mycelium,  was  present  in  types  1  to  4 
and  that  the  interior  of  figs  of  these  types  was  sterile.  Also  in  type  5 
no  positive  indications  of  smut  were  found  in  this  experiment.  In  types 
6  and  7  the  fungus  was  readily  detected.  During  the  four  days  com- 
mencing August  29,  1921,  6355  Adriatic  figs  were  gathered,  the  inside 


22  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

examined  by  a  hand  lens  and  results  checked  by  cultures.  The  findings 
were  the  same  as  in  the  last  experiments,  namely,  that  no  smut  fungus 
or  any  other  micro-organism  was  found  earlier  than  about  type  5,  after 
which  stage  the  figs  from  some  trees  showed  as  high  as  50  per  cent 
infection. 

On  September  2,  1921,  a  series  of  cultures  from  the  inside  of 
Adriatic  figs  of  the  different  types  was  started  to  study  further  the 
question  as  to  when  the  first  natural  introduction  of  smut  spores  occurs. 
Since  the  previous  cultures  had  shown  that  figs  of  the  first  four  types 
contained  no  smut,  this  experiment  was  confined  mainly  to  types  4,  5, 
and  6.  The  figs  were  cut  off  at  the  stem,  carried  at  once  to  the  labora- 
tory and  cultured  the  same  day.  Fig  agar  slants  were  ordinarily  used. 
All  the  usual  precautions  were  taken  to  avoid  the  possibility  of  smut 
spores  being  introduced  into  the  cultures  from  any  source  other  than 
the  fig  pulp  to  be  tested.  After  carefully  opening  each  fruit,  a  part  of 
the  pulp  just  below  the  eye,  but  not  in  contact  with  the  surface,  was 
cut  out  with  a  sterile  needle  and  transferred  to  the  culture  tube.  Five 
hundred  and  eight  tubes  from  as  many  different  figs  were  made  in  this 
manner,  with  results  as  before.  Figure  4  shows  typical  cultures  from 
the  pulp  of  figs  of  type  5.  Various  other  molds,  yeasts  and  bacteria 
were  also  present  and  the  abundance  of  these  showed  the  same  relation 
to  maturity  of  the  fruit  as  did  that  of  the  smut. 

In  1922  another  experiment  on  this  point  was  performed  in  a  some- 
what different  manner.  To  avoid  making  such  large  numbers  of  cul- 
tures, the  figs  were  simply  picked  from  the  trees  and  kept  for  several 
days  in  a  moist  chamber  at  high  summer  temperature  to  give  the  smut 
fungus  time  and  favorable  conditions  for  development  in  any  figs 
where  it  might  be  present.  In  other  words  the  fig  itself  served  as  a 
culture  tube.  The  fruit  was  then  opened  and  examined.  Seven  hun- 
dred and  thirty  Adriatic  figs  of  types  1  to  3  were  used  in  this  manner 
and  of  these  only  one  developed  the  smut  or  any  other  fungus  on  the 
inside,  and  this  was  near  the  eye  where  it  could  have  grown  in  from 
the  outside.  In  the  trees  from  which  these  figs  were  obtained,  smut 
was  present  in  considerable  abundance  in  the  mature  fruit. 

All  the  experiments  show  that  under  summer  conditions  in  the  San 
Joaquin  Valley  before  the  eye  of  the  Adriatic  fig  opens  and  the  fruit 
begins  to  soften  the  interior  cavity  is  sterile  and  neither  smut  spores 
nor  any  other  organisms  enter. 


Bull.  387J  FIG  SMUT  23 


IN  WHAT  PART  OF  THE  FIG  DOES  THE  INFECTION 
TAKE  PLACE 

Observation  of  the  occurrence  of  smut  in  figs,  together  with  the 
many  studies  and  experiments  described  in  this  bulletin,  leave  no  doubt 
that  it  is  on  the  inside  of  the  fig  that  infection  usually  occurs.  Figs 
confined  in  a  moist,  glass  chamber  or  dish,  or  simply  enclosed  in  a  cloth 
or  paper  sack  on  the  tree,  or  when  wet  by  rain,  are  sometimes  attacked 
and  caused  to  decay  from  the  outside  or  at  the  eye  by  various  molds. 
Under  normal,  summer  conditions,  however,  in  the  interior  valley,  figs 
on  the  tree  never  show  any  indication  of  smut  or  mold  infection  on  the 
surface,  but  only  from  the  inside. 


WHERE  DO  SMUT  SPORES  COME  FROM 

It  has  already  been  shown  that  the  smut  fungus  is  very  common  on 
decaying  fruit  of  all  kinds.  That  the  spores  of  the  fungus  are  also 
common  in  the  air,  was  shown  by  exposing  culture  plates  (Petri  dishes 
with  fig  agar)  in  fig  orchards  in  various  parts  of  the  San  Joaquin 
Valley.  Four  hundred  such  plates  were  exposed,  with  the  result  that 
Aspergillus  niger  appeared  upon  most  of  the  plates  as  a  common  mold, 
showing  that  the  spores  are  very  abundant  in  the  air.  Figure  5  shows 
one  of  these  plates  with  Aspergillus  and  other  molds  upon  it. 


HOW  DO  SMUT  SPORES  GET  INTO  THE  FIG 

This  is  a  very  important  consideration.  The  carrying  agencies 
which  suggest  themselves  as  most  probable  are  two,  namely,  air  cur- 
rents and  insects.  A  third  possible  factor,  moisture,  can  scarcely  be 
considered  of  general  importance  in  the  interior  valley,  on  account  of 
the  lack  of  precipitation  during  the  summer. 

WIND 

To  determine  whether  smut  spores  can  be  carried  into  figs  by  air 
currents,  the  following  experiment  was  made.  An  Adriatic  fig  tree 
which  showed  no  smut  was  chosen  for  inoculation.  Practically  every 
fig  of  types  4,  5,  and  6  within  reach  was  treated  by  puffing  out  a  cloud 


24  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

of  spores  from  a  smutted  fig  from  just  in  front  of  the  eye.  Wind  was 
blowing  at  the  time  and  the  fig  was  held  so  that  the  wind  borne  spores 
were  carried  toward  the  eye.  Many  of  the  eyes  were  black  with  the 
spores.  About  forty  figs  were  thus  treated  and  left  on  the  tree  until 
maturity.  When  examined  at  this  time,  no  sign  of  smut  was  found 
in  any  of  these  figs.  Our  observations  and  experience  in  inoculating 
figs  indicate  that  there  is  not  enough  moisture  for  the  spores  to  com- 
mence development  under  the  usual  summer  weather  conditions  of  the 
valley  unless  they  are  carried  well  into  the  eye  with  considerable 
physical  force  and  perhaps  scratched  into  the  pulp.  It  will  be  shown 
later,  however,  that  if  the  humidity  is  increased,  Aspergillus  and  other 
molds  develop  abundantly  on  the  outer  surface  of  the  fruit  and  may 
grow  through  the  eye  into  the  interior. 


Fig.  10. — The  dried  fruit  beetle  (Carpophilus  Jwmipterus)  which  lives  and 
breeds  in  ripening  figs  and  is  suspected  of  being  the  principal  infection  carrier 
of  smut  and  souring. 

INSECTS 

The  ripening  fig  with  its  almost  closed  interior  cavity  and  juicy, 
saccharine  pulp  furnishes  an  ideal  feeding  and  breeding  place  for 
certain  insects.  Flies,  bees,  wasps,  ants,  beetles,  and  other  sugar-loving 
insects  are  attracted  to  the  fig  orchard  at  harvest  season  in  great 
numbers.  These  ordinarily  feed  on  the  surface  of  overripe  or  decaying 
figs.  Other  insects  seek  the  inner  cavity  of  the  figs,  where  they  live 
and  breed  in  the  soft  flesh.  Decay  and  the  souring  or  fermentation 
which  occurs  very  commonly  in  ripe  figs  accompany  such  attacks  so 
regularly  that  it  is  often  thought  that  these  insects  feed  only  on  those 
figs  which  have  already  started  to  sour  or  rot.    When  many  figs  are 


Bull.  387]  FIG  SMUT  25 

examined,  however,  it  is  often  found  that  the  insects  are  present  in 
sound  fruit,  and  that  the  decay  or  souring  develops  afterward.  The 
insects  which  commonly  inhabit  the  interior  of  ripening  figs  are 
mainly  of  two  species,  the  vinegar  fly  (Drosophila  ampelophaga  Loew) 
and  the  dried  fruit  beetle  (CarpopJiilus  hemipterus  (Linn.)).  After 
the  ripening  of  the  figs  is  well  under  way,  it  is  easy  to  imagine  that 
these  insects  must  spread  all  forms  of  decay  and  fermentation,  since 
they  breed  in  great  numbers  in  the  spoiled  figs,  and  thence  enter  the 
sound  fruit  and  leave  a  trail  of  smut  and  other  spores  wherever  they 
go.  Pierce10  and  Hodgson8  suggest  the  possibility  of  parasitic 
organisms  being  spread  in  figs  by  insects. 

Dried  Fruit  Beetle. — Of  these  two  most  common  species,  the  dried 
fruit  beetle  (figs.  10  and  14)  is  more  especially  open  to  suspicion.  They 
are  present  from  the  very  beginning  of  maturity  in  sound  figs  and 
their  presence  is  always  correlated  with  the  development  of  the  spoilage 
of  the  fruit.  Howard11  (p.  94)  notes  the  common  occurrence  of  this 
insect  on  figs.  The  vinegar  fly  often  does  not  appear  until  the  season 
is  well  advanced.  The  beetles  crawl  indiscriminately  through  the  figs, 
good,  smutty,  or  sour,  spreading  the  organisms  which  cause  the  latter 
troubles.  They  also  breed  in  the  figs  as  they  hang  on  the  trees,  as  well 
as  after  they  fall  to  the  ground.  In  general,  the  beetle  shows  a  more 
constant  and  earlier  association  with  smut,  souring  and  all  the  similar 
troubles  than  any  other  insect.  In  the  few  cases  which  have  ever  been 
seen  of  an  Adriatic  fig  orchard  where  practically  all  the  fruit  was 
sound,  no  dried  fruit  beetles  could  be  found.  This  does  not  in  itself 
show  whether  these  insects  precede  or  are  attracted  by  the  development 
of  spoiled  fruit,  but  is  of  weight  when  viewed  in  connection  with  the 
other  known  facts.  Another  significant  observation  is  that  the  time 
when  smut  spores  and  souring  are  first  found  in  figs  (about  type  5,  as 
shown  in  previous  experiments)  is  the  time  that  the  eye  of  the  fruit 
begins  to  open,  the  flesh  softens  and  the  beetles  commence  to  enter. 
Another  fact  observed  is  that  vinegar  flies  are  not  often  found  at  all 
in  figs  of  the  first  crop,  but  smut,  souring,  and  beetles  are  often  found 
in  the  usual  correlation  in  this  crop  of  figs. 

It  is  a  simple  matter  to  prove  that  the  dried  fruit  beetles  in  the  fig 
orchard  are  carriers  of  smut  spores,  as  well  as  of  other  molds,  bacteria 
and  the  yeasts  which  accompany  souring.  Such  organisms  always 
develop  in  great  abundance  in  cultures  made  from  these  insects,  while 

io  Pierce,  Newton  B.  Investigations  of  the  Special  Agent  in  California. 
In  Kept.  Sec.  Agr.  1892:  238.     1893. 

n  Howard,  L.  O.  Smyrna  Fig  Culture  in  the  United  States.  In  Yearbook 
U.  S.  Dept.  Agr.  1900:  79-106.,  ill.     1901. 


26 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


ex 


Bull.  387]  FIG  SMUT  27 

beetles  taken  from  smutty  figs  are  covered  with  black  spore  dust  visible 
to  the  naked  eye.  To  determine  whether  this  is  the  sole  or  principal 
carrier,  is  not  so  easy.  The  most  obvious  method  would  be  to  exclude 
these  beetles  from  the  figs  in  some  way  and  observe  whether  smut  was 
thereby  prevented,  or  by  eliminating  all  other  insects  except  this  to  see 
if  smut  would  still  occur.  The  main  difficulty  in  doing  this  is  that 
almost  any  sort  of  insect-proof  covering  or  cage  increases  the  humidity 
and  this  produces  a  growth  of  molds  on  the  surface  of  figs  which  may 
penetrate  the  eye.  It  is  also  necessary  to  enclose  large  numbers  of  figs 
in  order  to  get  a  fair  average,  and  this  is  difficult  and  expensive. 
Enclosure  in  paper  or  cloth  bags  causes  molding  of  almost  all  of  the 
figs  and  is  therefore  unsatisfactory. 

In  an  attempt  to  accomplish  the  desired  result,  the  following  experi- 
ment was  made  in  1922.  Two  large  Adriatic  fig  trees  which  had  shown 
much  smut  the  previous  year  in  an  orchard  near  Fresno  were  covered 
with  unbleached  muslin,  supported  on  a  wooden  frame  (see  fig.  11). 
A  cloth  partition  separated  the  two  trees.  The  work  was  done  very 
carefully  in  order  to  keep  out  insects.  The  cloth  covering  was  put  on 
in  July  about  ten  days  before  any  figs  of  the  main  crop  had  commenced 
to  ripen  and  before  any  dried  fruit  beetles  appeared.  The  few  first 
crop  figs  on  these  trees  were  removed  and  a  very  careful  watch  was 
kept  throughout  the  experiment  for  the  presence  of  insects  within  the 
cages.  One  hundred  and  twelve  specimens  of  the  dried  fruit  beetle, 
taken  directly  from  sour  and  moldy  figs,  were  liberated  periodically  in 
tent  No.  2  from  August  25  to  October  5.  Nearly  all  of  these  flew  to 
the  tops  or  sides  of  the  tent  as  they  were  released  and  never  entered  the 
figs  in  the  usual  manner.  A  few  were  recovered  from  the  figs  picked 
up,  but  they  were  practically  absent  from  the  fruit  and  the  experiment 
was  therefore  a  failure  in  regard  to  testing  the  effect  of  the  beetle.  No 
vinegar  flies  were  found  in  the  tents  at  any  time  during  the  experi- 
ment and  only  a  very  few  other  insects,  none  of  which  would  be  likely 
to  attack  figs.  A  particular  effort  was  made  throughout  the  season  to 
keep  tent  No.  1  free  from  insects  of  any  kind.  The  figs  in  both  tents 
were  picked  up  and  examined  throughout  the  ripening  season  as  fast 
as  they  fell  to  the  ground.  More  than  sixteen  thousand  figs  were 
handled  in  this  manner.  Temperature  and  humidity  records  were 
taken  and  showed  that  the  temperature  in  the  tents  was  somewhat  lower 
than  outside  and  the  humidity  greater.  Condensed  moisture  on  the 
fruit  and  foliage  was  frequently  noticed  under  the  tents. 

The  most  striking  result  of  this  experiment  was  that  no  souring 
occurred  in  either  tent,  although  it  was  abundant  on  all  the  neighbor- 


28 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


ing  trees  outside.  The  smut  fungus,  A.  niger,  was  very  abundant  in 
both  tents,  but  so  far  as  could  be  determined  always  started  on  the 
outside  or  at  the  eye  of  the  figs,  along  with  many  other  molds.  In 
fact,  the  moisture  condition  inside  of  the  tent  was  so  favorable  to  the 
growth  of  molds  that  no  conclusions  could  be  drawn  as  to  the  effect  on 
smut  of  excluding  insects.  A  fact  of  interest  was  the  splitting  of  a 
large  number  of  figs  under  the  tent,  while  outside  no  splitting  was 
noticed  in  this  orchard.    The  experiment  was  not  conclusive  in  regard 


Fig.  12. — Cull  oranges  on  ground  beneath  tree,  furnishing  ideal  breeding  and 
wintering-over  place  for  dried  fruit  beetles  and  fungi.    Photo  by  Condit. 


to  normal  smut  infection,  but  showed  that  enclosing  the  figs  within  the 
tent  in  some  way  prevented  souring.  The  common  idea  that  high 
humidity  causes  souring,  was  disproven.  To  carry  out  the  original 
purpose  of  this  experiment  successfully,  a  method  must  be  found  to 
exclude  or  confine  the  insects  at  will,  without  changing  the  normal 
humidity,  temperature,  or  light  conditions  too  greatly. 

Further  Investigations  on  the  Relations  Between  Fig  Diseases  and 
the  Dried  Fruit  Beetle. — The  indication  that  an  important  relation 
exists  between  the  dried  fruit  beetle  and  the  dissemination  of  fig  smut 


Bull.  387] 


FIG    SMUT 


29 


Fig.  13. — Old  melons  in  field  near  fig  orchard,  furnishing  abundant  supply 
of  dried  fruit  beetles  and  fungi.    Photo  by  Condit. 


30  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

and  decay  organisms  led  to  further  study  of  the  habits  of  this  insect. 
The  beetle  does  not  confine  itself  to  dried  fruit  in  the  packing  house,  or 
elsewhere,  but  is  found  wherever  any  old  fruit  is  allowed  to  accumulate, 
if  the  fruit  does  not  become  too  dry.  Either  or  both  the  adults  or 
larvae  of  these  beetles  have  been  found  in  the  following  material  at 
the  time  of  year  stated. 

November-March — 

Figs,  all  kinds  and  conditions. 

Melons,  fermenting  and  molding  (fig.  13). 

Apples,  rotting  on  ground. 
April — 

Prunes,  old,  in  packing  house. 

Apples,  in  dump  and  under  trees. 

Oranges,  on  ground  under  trees  (fig.  12). 

Melons,  decaying  in  field. 
May- 
Oranges,  on  ground  under  trees. 

Figs,  old  culls  in  dry  yard. 
June — 

Figs,  old  culls  in  orchard. 

Oranges,  on  ground  under  trees. 

Grapefruit,  culls  on  ground. 
July- 
Figs,  Cordelia  variety,  fresh,  ripe,  sound,  and  sour. 
Mission,  moldy,  first  crop  on  ground  under  tree. 
Old  culls  on  ground  near  fig  orchard. 
Brunswick  variety,  first  crop,  some  sour. 
Adriatic  variety,  first  crop,  both  sound  and  sour. 
Kadota  variety,  first  crop,  sour. 

Peaches,  ripe,  on  ground. 

Apricots,  ripe,  rotted  by  smut  fungus. 

Tomatoes,  ripe  and  moldy. 

August — 

Apples,  rotting  on  ground,  infested  with  worms,  and  various  molds, 

including  smut  fungus. 
Melons,  fermenting  and  moldy,  smut  fungus  present. 
Figs,  Adriatic  variety,  sound,  souring,  moldy,  and  smutty. 

Kadota  variety,  both  sound  and  sour. 
Peaches,  fermenting  and  rotting,  smut  fungus  present. 
Plums,  like  peaches. 
Pears,  wormy,  rotting,  and  fermenting. 
September — 

Figs,  Calimyrna,  Kadota,  and  Adriatic  varieties,  sound,  souring, 
rotting,  moldy,  and  smutty,  both  on  trees  and  ground. 
October — 

Figs  and  other  fruits,  all   kinds  and   conditions,  many  souring, 
moldy,  and  smutty. 


Bull.  387] 


PIG  SMUT 


31 


0 


~  % 


Fig.  14. — Carpophilus  Jiemipterus  and  other  small  beetles  issuing  from  decaying 
orange,  covered  with  disease  germs  and  ready  to  attack  first  ripe  figs. 


32  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

In  addition  to  its  occurrence  on  figs  and  the  other  substances  men- 
tioned in  the  above  list,  the  smut  fungus,  Aspergillus  niger,  was  found 
in  1922  growing  on  straw,  melon  rinds,  grapes,  and  on  moist  soil 
adjacent  to  fallen  figs.  All  of  these  supported  an  abundant,  active 
growth. 

Blister  Mite. — During  the  course  of  this  work  there  was  discovered 
a  new  species  of  blister  mite  (Eriophyes  fici  Ewing)  occurring  abun- 
dantly on  the  inside  of  figs  of  all  varieties.12  These  mites  are  of 
microscopic  size,  being  practically  invisible  to  the  eye,  and  cause 
browning  of  the  scales  and  florets  inside  the  fig.  They  spend  the 
winter  in  the  buds  and  enter  the  young  figs  when  they  are  very  small. 
No  form  of  infection  is  commonly  transmitted  by  these  mites  since  they 
are  present  even  in  very  small  green  fruit,  the  inside  of  which  is  sterile 
up  to  about  type  4  or  5  (figs.  6  and  7)  and  until  insects  have  entered. 
This  was  shown  in  the  experiments  described  on  page  21  in  which  the 
interior  of  about  8000  Adriatic  figs  of  different  stages  of  maturity  was 
examined  and  cultured.  Mites  were  present  in  virtually  all  of  these 
figs.  A  record  was  kept  of  those  which  showed  the  most  pronounced 
signs  of  mite  injury,  -and  cultures  showed  that  there  were  as  many 
sterile  figs  among  these  as  in  the  others.  Since  all  figs  previous  to 
type  4  were  found  to  be  sterile,  and  very  few  of  types  4  and  5  developed 
smut  or  other  infections,  it  was  evident  that  in  the  figs  examined,  the 
blister  mite  played  no  important  part  in  introducing  fungous  spores. 

Other  Insects. — In  addition  to  the  fruit  beetle  and  vinegar  fly, 
several  insects  have  been  found  rather  commonly  on  figs,  but  not  with 
enough  regularity  or  abundance  to  suggest  any  importance  in  the 
transmission  of  diseases.  Small  beetles,  identified  by  Prof.  E.  0. 
Essig  as  Notoxus  constrictus  Casey,  Cnemeplatia  sericea  Horn  (fig. 
15),  and  Blapstinus  fuliginosus  Casey,  attack  figs  on  the  ground  in 
limited  numbers.  Ants  are  common,  but  have  never  been  noticed  in 
tiers  on  the  tree. 


12  Essig,  E.  O.,  and  Smith,  Elizabeth  H.     Two  Interesting  New  Blister  Mites. 
In  Monthly  Bull.  Cal.  State  Dept.  Agr.  11:  63.     1922. 

Essig,  E.  O.     Notes  on  the  Two  New  Blister  Mites.     Ibid.,  11:  466.     1922. 


Bull.  387]  FIG   SMUT  33 


CONTROL  OF  SMUT 

SPRAYING 

The  possibility  of  controlling  smut  by  spraying  the  trees,  has  been 
tested.  This  work  has  also  afforded  an  opportunity  to  determine 
whether  or  not  similar  treatment  would  control  other  fig  troubles  such 
as  souring  and  various  forms  of  rot.  No  success  whatever  has  been 
obtained  by  this  method  of  treatment,  as  might  be  expected  after  the 


Fig.  15. — First  crop  Adriatic  figs  showing  work  of  Cnemeplatia  sericea, 
a  small  beetle  of  minor  importance. 

nature  of  these  diseases  and  the  manner  in  which  they  are  introduced 
into  the  figs  is  understood.  Pierce10  reports  similar  results,  and  for 
the  same  reasons,  in  his  early  attempts  to  control  fig  troubles  by 
spraying. 

In  1922  B.  A.  Rudolph  of  the  Division  of  Plant  Pathology  tried 
the  applications  of  dormant  winter  sprays  and  also  treatment  just  as 
the  buds  were  opening  in  the  spring.  Both  fungicides  and  insecticides 
were  used,  the  latter  being  specially  designed  to  control  the  blister 
mite.  Spraying  was  done  as  shown  in  the  following  table  in  an  orchard 
near  Fresno  of  Adriatic  figs  which  had  shown  a  considerable  amount  of 
smut  and  a  large  amount  of  souring  the  previous  year. 


34 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig  Spraying  Experiments  in  1922 


No. 

Spray 

Time 

1 

Crude  Oil  Emulsion  30  gals.,  dry  lime-sulfur 

48  lbs.,  water  170  gals. 

January   19,  1922 

2 

Crude  Oil  Emulsion  30  gals.,  dry  Bordeaux 
mixture  48  lbs.,  water  170  gals. 

January   19,   1922 

3 

Dry  Bord 
water 

leaux  mixture  40  lbs., 
100  gals. 

January   16,  1922 

4 

Dry  lime- 
water 

sulfur  48  lbs., 
200  gals. 

January  14,  1924 

5 

Dry  lime 
water 

-sulfur  24  lbs., 
200  gals. 

March  25,  1922 

6 

Dry  lime- 
water 

sulfur  12  lbs., 
200  gals. 

March  25,   1924 

7 

Dry  Bordeaux  mixture  32  lbs., 
water  200  gals. 

March  25,   1924 

8 

1  plus  5, 

as  above 

9 

1  plus  7, 

as  above 

10 

2  plus  5, 

as  above 

11 

2  plus  7, 

as  above 

12 

3  plus  5, 

as  above 

13 

3  plus  6, 

as  above 

14 

4  plus  6, 

as  above 

At  the  time  when  the  January  application  was  made,  the  leaves 
were  all  off  and  the  trees  dormant.  When  the  spraying  was  done  in 
March,  the  buds  were  just  opening  for  the  new  season's  growth.  The 
table  shows  that  some  trees  received  the  dormant  spray  alone,  some 
the  spring  application  with  no  other  treatment,  while  others  received 
combinations  of  the  various  mixtures  at  the  two  different  times  of 
application. 

None  of  these  treatments  showed  enough  effect  on  the  amount  of 
smut,  souring,  or  any  other  disease  or  pest  during  the  following  season 
to  be  considered  significant.  No  definite  counts  or  measurements  were 
completed,  as  all  the  sprayed  trees  developed  an  abundance  of  the 
usual  troubles. 

During  1923,  summer  spraying  was  tried  at  various  points  in  the 
San  Joaquin  Valley,  the  work  being  done  by  Messrs.  J.  P.  Martin  and 
P.  D.  Caldis  of  the  Division  of  Plant  Pathology  in  cooperation  with 
the  Fig  Growers'  Association  and  various  individual  growers.  Blocks 
of  trees  were  sprayed  in  sixteen  different  orchards  located  at  various 


Bull.  387]  FIG  SMUT  35 

points  from  Modesto  (Stanislaus  County)  on  the  north,  to  Strathmore 
(Tulare  County)  on  the  south.  In  this  case,  all  the  spraying  was 
done  with  the  following  mixture : 


Dry  lime-sulfur 8  lbs. 

"Kayso"  (Calcium  casemate)  2  lbs. 

Water    200  gals. 

Both  Calimyrna  and  Adriatic  figs  were  sprayed.  Most  of  the 
spraying  was  done  in  the  latter  part  of  July  just  before  the  time  when 
the  figs  reached  maturity  and  smut,  rot,  and  souring  usually  com- 
mence, and  as  late  as  it  was  thought  possible  to  spray  without  leaving 
too  much  visible  residue  upon  the  mature  fruit.  No  effect  could  be 
seen  from  any  of  this  work,  since  rot,  souring,  and  smut  were  present 
on  the  sprayed  trees  in  average  amounts.  There  was  an  excessive 
amount  of  spoilage  in  figs  in  1923,  so  that  the  non-effect  of  the  spraying 
was  very  evident. 

The  above  described  summer  treatment  was  suggested  by  the  success 
reported  by  some  growers  from  such  an  application.  It  appears,  how- 
ever, that  apparent  results  from  spraying  and  other  treatment  of  figs 
in  controlling  various  forms  of  decay  have  hitherto  been  based  upon 
treatment  of  fruit  which  was  picked  in  a  fresh  condition,  rather  than 
that  which  was  allowed  to  reach  full  maturity  and  fall  to  the  ground 
for  drying.  When  figs  are  picked  fresh,  much  of  the  rot  has  only 
just  started  to  develop  and  the  fruit,  therefore,  appears  to  be  free 
from  these  troubles.  It  is  only  by  allowing  the  figs  to  remain  on  the 
trees  until  they  reach  full  maturity  that  a  correct  estimate  can  be 
obtained. 

FERTILIZATION  AND  SOIL  TREATMENT 

It  has  often  been  suggested  that  by  keeping  the  soil  in  good  condi- 
tion, or  by  applying  lime  or  some  other  chemical  substance  to  the 
ground,  troubles  like  smut  and  souring  might  be  controlled.  In  order 
to  test  this,  experiments  were  conducted  in  cooperation  wHh  the  Fig 
Growers'  Association.  Nine  typical  fig  orchards  were  selected  in 
Fresno,  Merced  and  Stanislaus  counties  and  applications  made  to 
different  blocks  of  trees  with  the  following  materials:  lime  (air 
slaked),  1500  lbs.  per  acre;  sulfur,  400  lbs.  per  acre;  horse  manure, 
10,000  lbs.  per  acre ;  gypsum,  1400  lbs.  per  acre ;  ammonium  sulfate, 
6  lbs.  per  tree ;  blood  meal,  6  lbs.  per  tree ;  bean  straw ;  nitrate  of  soda, 
400  lbs.  per  acre ;  superphosphate,  400  lbs,  per  acre.  The  quantities 
stated    are    the    maximums   which   were   used   with    each   substance. 


36  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Smaller  quantities  and  various  combinations  of  the  different  materials 
were  also  tried.  These  applications  were  made  in  the  spring  of  1922 
and  repeated  on  the  same  plots  in  1923.  Up  to  date  (1924)  no  striking 
influence  can  be  seen  from  the  use  of  any  of  the  substances  tested  upon 
the  amount  of  smut  or  souring,  or  even  upon  the  appearance  of  the 
trees.  The  gathering  of  exact  data  upon  the  results  of  these  experi- 
ments has  not  been  carried  out  on  account  of  this  evident  lack  of 
effect. 

SANITATION 

The  only  apparent  hope  of  control  of  smut  and  other  fig  troubles 
due  to  fungi  transmitted  from  decaying  fruit  by  scavenger  insects,  lies 
in  the  elimination  of  such  fruit  and  insects  from  the  vicinity  of  the 
orchard.  It  is  strongly  recommended  that  all  fruit,  such  as  cull 
oranges  and  melons,  should  be  cleaned  up  in  the  winter  time,  while  in 
summer,  just  before  the  figs  commence  to  ripen,  everything  that  might 
harbor  molds  and  fruit-decay  insects  should  be  destroyed.  (See 
Phillips13.) 

IMMUNE  VARIETIES 

The  fact  has  already  been  mentioned  that  there  is  a  difference  in 
the  susceptibility  of  the  different  fig  varieties  to  smut.  Of  the  four 
varieties  commonly  grown  in  California,  the  Calimyrna  and  Adriatic 
are  most  susceptible,  while  the  Black  Mission  and  Kadota  are  much 
less  commonly  affected.  It  is  significant  that  the  same  difference  of 
susceptibility  holds  true  in  regard  to  souring  and  some  of  the  other 
rots.  The  reason  for  this  immunity  of  the  Mission  and  Kadota  was 
studied.  First  of  all,  it  must  be  stated  that  these  varieties  are  not 
entirely  immune.  The  fact  remains,  however,  that  we  seldom  see  them 
affected  by  A.  niger,  or  any  other  fungus  under  normal  summer 
climatic  conditions  in  the  San  Joaquin  Valley.  Inoculations  of  figs  of 
these  varieties  in  all  types  were  made  with  the  smut  fungus,  using  a 
pure  culture  from  an  Adriatic  fig.  After  the  inoculation,  rotting  took 
place  just  as  in  the  Adriatic  and  Calimyrna,  showing  that  the  Mission 
and  Kadota  are  not  resistant  to  the  smut  fungus  after  it  once  gets  in. 
The  very  solid  nature  of  the  fruit  and  closed  eye  seem  to  explain  the 
immunity  of  these  varieties.  While  an  Adriatic  fig  presents  a  hollow, 
juicy  interior,  the  fruit  of  the  Mission  and  Kadota  is  nearly  always 
filled  out  solid  to  the  eye.    The  former  conditions  are  very  enticing  to 


is  Phillips,  Edith  H.     Checking  Fig  Smut.     In  Associated  Grower  5:  no.  2,  10. 
1923. 


Bull.  387]  FIG  SMUT  37 

insects  and  offer  more  chance  even  to  air-borne  infection ;  the  latter 
conditions  are  unfavorable  to  both  methods  of  infection.  The  Mission 
and  Kadota  also  have  a  small,  closed  eye,  making  it  difficult  for  any 
of  the  usual  insects  except  the  Blastophaga  to  get  into  the  fig.  Growers 
often  say  that  if  they  had  a  white  Mission — that  is,  a  fig  with  all  the 
other  qualities  of  the  Black  Mission,  but  of  white  color — the  problem 
would  be  solved.  The  possibility  of  obtaining  such  a  variety  is  attrac- 
tive and  a  start  has  been  made  in  this  direction.  In  1921  a  quantity  of 
fig  seed  was  gathered  from  Mission  and  Kadota  trees  on  which  the 
fruit  had  been  pollinized  from  nearby  caprifigs.  This  seed  was 
planted  in  the  spring  of  1922  and  a  considerable  number  of  seedlings 
secured.  These  trees,  representing  crosses  between  capri  and  Mission 
and  capri  and  Kadota,  are  now  being  grown  in  orchard  form  to  ascer- 
tain what  type  of  fruit  they  will  produce.  In  1922  other  crosses  were 
made  by  hand-pollinizing  Mission  and  Kadota  with  certain  capris 
having  large  fleshy  fruit.  These  capri  figs  were  some  of  the  so-called 
Maslin  seedlings,  which  are  themselves  seedlings  of  Smyrna  figs. 
Seedlings  from  these  crosses  are  also  now  growing  in  orchard  form. 


CONCLUSIONS 

Fig  Smut  is  caused  by  the  fungus  Aspergillus  niger.  This  is  a  very 
common  mold  of  universal  occurrence  on  decaying  vegetable  matter. 

The  fig  smut  fungus  is  not  a  special  strain  of  A.  niger. 

Figs  become  infected  with  smut  when  they  are  still  on  the  tree, 
just  at  the  time  when  the  eye  opens  and  the  fruit  begins  to  soften.  No 
infection  occurs  much  before  or  after  this  stage. 

Typical  smut  infection  takes  place  on  the  inside  of  the  fruit  only. 

In  the  climate  of  the  San  Joaquin  Valley,  the  interior  cavity  of 
Adriatic  figs  usually  remains  sterile  until  it  has  been  entered  by 
insects. 

The  smut  fungus  is  usually  carried  into  figs  by  insects,  of  which 
the  dried  fruit  beetle,  Carpophilus  hemipterus  (Linn.)  appears  to  be 
the  most  important. 

Indications  point  to  the  dried  fruit  beetle  as  being  also  an  important 
carrier  of  some  other  forms  of  decay.  The  vinegar  fly  (Drosophila 
ampelophaga  (Loew)  is  probably  second  in  importance. 

The  beetle  lives  throughout  the  year  on  various  decaying  fruits, 
which  also  breed  vinegar  flies  and  harbor  the  germs  of  smut  and  other 
forms  of  rot  in  figs. 


38  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Spraying,  either  in  winter  or  summer,  with  insecticides  or  fungi- 
cides, had  no  appreciable  effect  in  controlling  smut  or  any  other  of  the 
fig  troubles  observed. 

Soil  fertilization  was  also  of  no  avail. 

The  destruction  of  the  dried  fruit  beetle  and  insects  of  similar 
habits  seems  very  promising  for  the  control  of  smut. 

Good  orchard  sanitation  is  the  best  method  known  at  present  for 
accomplishing  this.  This  consists  in  cleaning  up  all  old  fruit,  fruit 
culls  and  refuse  on  which  such  insects  as  the  dried  fruit  beetle  and 
vinegar  fly  might  breed. 

The  Black  Mission  and  Kadota  varieties  are  much  less  affected  by 
smut,  souring  and  similar  troubles  than  the  Calimyrna  and  Adriatic. 

This  immunity  of  the  Mission  and  Kadota  seems  to  be  due  to  the 
exclusion  of  insects  from  the  inside  of  these  figs  by  their  solid  structure 
and  closed  eye,  rather  than  to  any  real  resistance. 

It  may  be  possible  to  obtain  a  desirable,  immune,  white  fig  by 
breeding. 


STATION  PUBLICATIONS  AA^AILABLE  FOR  FREE  DISTRIBUTION 


BULLETINS 
No.  No. 

253.   Irrigation   and    Soil  Conditions  in  the  352. 

Sierra  Nevada  Foothills,  California. 

261.  Melaxuma    of    the    Walnut,     "Juglans  353. 

regia."  354. 

262.  Citrus   Diseases   of  Florida   and   Cuba  357. 

Compared  with  Those  of  California. 

263.  Size  Grades  for  Ripe  Olives. 

268.   Growing  and  Grafting  Olive  Seedlings.  358. 

273.   Preliminary  Report  on  Kearney  Vine- 
yard Experimental  Drain.  359. 

275.  The  Cultivation  of  Belladonna  in  Cali-  361. 

fornia. 

276.  The  Pomegranate.  362. 

277.  Sudan  Grass  363. 

278.  Grain  Sorghums. 

279.  Irrigation  of  Rice  in  California.  364. 

280.  Irrigation  of  Alfalfa  in  the  Sacramento 

Valley.  366. 

283.  The  Olive  Insects  of  California. 

285.  The  Milk  Goat  in  California.  367. 

286.  Commercial  Fertilizers. 

294.   Bean  Culture  in  California.  368. 

304.  A   Study  of  the  Effects  of  Freezes  on 

Citrus   in   California.  369. 

310.  Plum  Pollination.  370. 

312.  Mariout  Barley.  371. 

313.  Pruning  Young  Deciduous  Fruit  Trees. 

319.   Caprifigs  and  Caprification.  372. 

324.  Storage  of  Perishable  Fruit  at  Freezing 

Temperatures.  374. 

325.  Rice  Irrigation  Measurements  and  Ex- 

periments    in      Sacramento     Valley, 
1914-1919.  375. 

328.   Prune  Growing  in  California. 

331.   Phylloxera-Resistant  Stocks.  376. 

334.  Preliminary  Volume  Tables  for  Second- 

Growth  Redwood.  377. 

335.  Cocoanut    Meal    as    a    Feed   for   Dairy  3  79. 

Cows  and  Other  Livestock.  380. 

339.  The  Relative  Cost  of  Making  Logs  from 

Small  and  Large  Timber.  381. 

340.  Control  of  the  Pocket  Gopher  in  Cali- 

fornia. 382. 

343.  Cheese  Pests  and  Their  Control. 

344.  Cold  Storage  as  an  Aid  to  the  Market-  383. 

ing  of  Phims. 

346.  Almond  Pollination.  384. 

347.  The  Control  of  Red  Spiders  in  Decidu- 

ous Orchards. 

348.  Pruning  Young  Olive  Trees.  385. 

349.  A    Study    of    Sidedraft    and    Tractor  386. 

Hitches. 

350.  Agriculture  in  Cut-over  Redwood  Lands. 


Further  Experiments  in  Plum  Pollina- 
tion. 

Bovine  Infectious  Abortion. 

Results  of  Rice  Experiments  in   1922. 

A  Self-mixing  Dusting  Machine  for 
Applying  Dry  Insecticides  and 
Fungicides. 

Black  Measles,  Water  Berries,  and 
Related  Vine  Troubles.  ■ 

Fruit  Beverage  Investigations. 

Preliminary  Yield  Tables  for  Second 
Growth  Redwood. 

Dust  and  the  Tractor  Engine. 

The  Pruning  of  Citrus  Trees  in  Cali- 
fornia. 

Fungicidal  Dusts  for  the  Control  of 
Bunt. 

Turkish  Tobacco  Culture,  Curing  and 
Marketing. 

Methods  of  Harvesting  and  Irrigation 
in  Relation  to  Mouldy  Walnuts. 

Bacterial  Decomposition  of  Olives  dur- 
ing Pickling. 

Comparison  of  Woods  for  Butter  Boxes. 

Browning  of  Yellow  Newtown  Apples. 

The  Relative  Cost  of  Yarding  Small 
and  Large  Timber. 

The  Cost  of  Producing  Market  Milk  and 
Butterfat  on  246  California  Dairies. 

A  Survey  of  Orchard  Practices  in  the 
Citrus  Industry  of  Southern  Cali- 
fornia. 

Results  of  Rice  Experiments  at  Cor- 
tena,    1923. 

Sun-Drying  and  Dehydration  of  Wal- 
nuts. 

The  Cold  Storage  of  Pears. 

Walnut  Culture  in  California. 

Growth  of  Eucalyptus  in  California 
Plantations. 

Growing  and  Handling  Asparagus 
Crowns. 

Pumping  for  Drainage  in  the  San 
Joaquin  Valley,   California. 

Monilia  Blossom  Blight  (Brown  Rot) 
of  Apricot. 

A  Study  of  the  Relative  Values  of  Cer- 
tain Succulent  Feeds  and  Alfalfa  Meal 
as  Sourses  of  Vitamin  A  for  Poultry. 

Pollination  of  the  Sweet  Cherry. 

Pruning  Bearing  Deciduous  Fruit 
Trees. 


No. 

87.  Alfalfa. 
113.   Correspondence  Courses  in  Agriculture. 
117.  The    Selection    and    Cost    of    a    Small 

Pumping  Plant. 
127.  House  Fumigation. 
129.  The  Control  of  Citrus  Insects. 
136.  Melilotus    indica    as    a    Green-Manure 

Crop  for  California. 
144.    Oidium  or  Powdery  Mildew  of  the  Vine. 

151.  Feeding  and  Management  of  Hogs. 

152.  Some  Observations  on  the  Bulk  Hand- 

ling of  Grain  in  California. 
154.   Irrigation   Practice   in   Growing  Small 
Fruit  in  California. 


CIRCULARS 

No. 


155.   Bovine  Tuberculosis. 
157.   Control  of  the  Pear  Scab. 

160.  Lettuce  Growing  in  California. 

161.  Potatoes  in  California. 

164.  Small  Fruit  Culture  in  California. 

165.  Fundamentals   of   Sugar   Beet   Culture 

under  California  Conditions. 

166.  The  County  Farm  Bureau. 

167.  Feeding  Stuffs  of  Minor  Importance. 
170.   Fertilizing  California  Soils  for  the  1918 

Crop. 
173.  The    Construction    of    the   Wood-Hoop 

Silo. 
178.  The  Packing  of  Apples  in  California. 


CIRCULARS — (Continued) 


No. 

179.   Factors    of    Importance    in    Producing 

Milk  of  Low  Bacterial  Count. 
184.  A  Flock  of  Sheep  on  the  Farm. 
190.  Agriculture  Clubs  in  California. 
199.   Onion  Growing  in  California. 

202.  County    Organizations   for    Rural    Fire 

Control. 

203.  Peat  as  a  Manure  Substitute. 

208.  Summary  of  the  Annual  Reports  of  the 

Farm  Advisors  of  California. 

209.  The  Function  of  the  Farm  Bureau. 

210.  Suggestions  to  the  Settler  in  California. 
212.    Salvaging  Rain-Damaged  Prunes. 

214.  Seed  Treatment  for  the  Prevention  of 

Cereal  Smuts. 

215.  Feeding  Dairy  Cows  in  California. 
217.   Methods   for   Marketing   Vegetables   in 

California. 
220.    Unfermented  Fruit  Juices. 
228.   Vineyard  Irrigation  in  Arid  Climates. 

231.  The  Home  Vineyard. 

232.  Harvesting    and    Handling    California 

Cherries  for  Eastern   Shipment. 

233.  Artificial  Incubation. 

234.  Winter  Injury  to  Young  "Walnut  Trees 

during  1921-22. 

235.  Soil  Analysis  and  Soil  and  Plant  Inter- 

relations. 

236.  The  Common  Hawks  and  Owls  of  Cali- 

fornia   from    the    Standpoint    of    the 
Rancher. 

237.  Directions  for  the  Tanning  and  Dress- 

of  Furs. 

238.  The  Apricot  in  California. 

239.  Harvesting  and  Handling  Apricots  and 

Plums  for  Eastern  Shipment. 

240.  Harvesting    and    Handling    Pears   for 

Eastern   Shipment. 

241.  Harvesting  and  Handling  Peaches  for 

Eastern   Shipment. 

243.  Marmalade  Juice  and  Jelly  Juice  from 

Citrus  Fruits. 

244.  Central  Wire  Bracing  for  Fruit  Trees. 

245.  Vine  Pruning  Systems. 

247.  Colonization  and  Rural  Development. 

248.  Some  Common  Errors  in  Vine  Pruning 

and  Their  Remedies. 

249.  Replacing  Missing  Vines. 

250.  Measurement    of    Irrigation    Water   on 

the  Farm. 


No. 

251.  Recommendations  Concerning  the  Com- 

mon    Diseases     and     Parasites     of 
Poultry  in  California. 

252.  Supports   for  Vines. 

253.  Vineyard  Plans. 

254.  The  Use  of  Artificial  Light  to  Increase 

Winter  Egg  Production. 

255.  Leguminous   Plants  as  Organic  Fertil- 

izer in   California  Agriculture. 

256.  The  Control  of  Wild  Morning  Glory. 

257.  The  Small-Seeded  Horse  Bean. 

258.  Thinning  Deciduous  Fruits. 

259.  Pear  By-products. 

260.  A  Selected  List  of  References  Relating 

to  Irrigation  in  California. 

261.  Sewing  Grain   Sacks. 

262.  Cabbage  Growing  in  California. 

263.  Tomato   Production  in  California. 

264.  Preliminary  Essentials  to  Bovine  Tuber- 

culosis Control. 

265.  Plant  Disease  and  Pest  Control. 

266.  Analyzing  the  Citrus  Orchard  by  Means 

of  Simple  Tree  Records. 

267.  The  Tendency  of  Tractors  to  Rise  in 

Front;  Causes  and  Remedies. 

268.  Inexpensive  Lavor-saving  Poultry  Ap- 

pliances. 

269.  An  Orchard  Brush  Burner. 

270.  A  Farm  Septic  Tank. 

271.  Brooding  Chicks  Artificially. 

272.  California  Farm  Tenancy  and  Methods 

of  Leasing. 

273.  Saving  the  Gophered  Citrus  Tree. 

275.  Marketable        California        Decorative 

Greens. 

276.  Home  Canning. 

277.  Head,   Cane,   and  Cordon   Pruning  of 

Vines. 

278.  Olive  Pickling  in  Mediterranean  Coun- 

tries. 

279.  The  Preparation  and  Refining  of  Olive 

Oil  in  Southern  Europe. 

281.  The  Results  of  a  Survey  to  Determine 

the  Cost  of  Producing  Beef  in  Cali- 
fornia. 

282.  Prevention  of  Insect  Attack  on  Stored 

Grain. 


The  publications  listed  above  may  be  had  by  addressing 

College  of  Agriculture, 

University  of  California, 

Berkeley,  California. 


lOw-4,'25 


